Vettel fastest in morning session as McLaren hits trouble

MONTMELO, Spain -- Sebastian Vettel topped the opening morning of the second week of Formula One testing while McLaren struggled for mileage due to electrical issues.

Freezing temperatures, rain and snow meant all ten teams finished the first week of testing with long to-do lists for week two, but with Europe's unseasonal cold front returning tothe north, the Circuit de Catalunya was left basking in warmer temperatures on Tuesday morning.

Ferrari, Mercedes and Red Bull all completed over 80 laps in the morning session, with only McLaren struggling to make the most of the better conditions. Things started badly when Stoffel Vandoorne returned from his installation lap without power -- a problem McLaren later confirmed was an electrical shutdown of the power unit.

After just over an hour in the pits, Vandoorne emerged on track again only to complete two more laps before the Renault power unit -- and its telemetry being fed back to the pits -- cut out as he arrived on the pit straight to complete the third lap of his run. The car had to be pushed back down to the McLaren garage at the other end of the pit lane where it remained until the final minutes of the morning session when Vandoorne returned to the track for three further laps.

Despite the improved conditions, the times at the top were still over a second off the best effort set by Lewis Hamilton on Thursday last week. Vettel's quickest time of 1:20.396 was set on the medium compound tyre and was 0.200s clear of Valtteri Bottas' fastest lap using the soft compound. Max Verstappen was a further 0.053s off in the Red Bull using the mediums. But with times expected to drop into the 1:17s by the end of the week, there is still plenty of performance to be unlocked for all three teams.

Elsewhere, Pierre Gasly completed another solid morning in the Toro Rosso-Honda with over 50 laps and the fourth fastest time. Kevin Magnussen was fifth fastest for Haas ahead of Nico Hulkenberg's Renault, Sergey Sirotkin in the Williams, Marcus Ericsson in the Sauber and Sergio Perez for Force India.

Lewis Hamilton is scheduled to take over the Mercedes in the afternoon while Carlos Sainz will replace Hulkenberg at Renault, Brendon Hartley will replace Pierre Gasly at Toro Rosso and Lance Stroll will drive the Williams.

Times at lunch:
1. Vettel, Ferrari, 1:20.396, 86 laps (Medium)
2. Bottas, Mercedes, 1:20.596, 86 laps (Soft)
3. Verstappen, Red Bull, 1:20.649, 85 laps (Medium)
4. Gasly, Toro Rosso, 1:20.973, 53 laps (Soft)
5. Magnussen, Haas, 1:21.298, 46 laps (Soft)
6. Hulkenberg, Renault, 1:21.432, 48 laps (Medium)
7. Sirotkin, Williams, 1:21.588, 42 laps (Soft)
8. Ericsson, Sauber, 1:21.893, 56 laps (Soft)
9. Perez, Force India, 1:21.936, 37 laps (Soft)
10. Vandoorne, McLaren, 1:24.773, 7 laps (Super-soft)